PESTS.
Orchids generally do not suffer from the usual plethora
of ailments which affect many of our favorite garden
plants, this is for two reasons, firstly many of the
species and hybrids we grow are alien to our local
atmosphere, and consequently also alien to many pests
and diseases we find outdoors, and the second one is
that because of the fact that we grow them mainly
indoors they are not exposed to the problem in the first
place.
Unfortunately, when a problem occurs it can be difficult
to eradicate once is gains a foothold.

Here are a few, in no particular order:-

Slugs, even if you think you haven't got any problem
with these night-time assassins, you should always be
vigilant for their silvery trails, sprinkle at regular
intervals with a good slug liquid, and if you feel
adventurous, take a torch-light trip into the growing
area after dark, a good well aimed boot is something
they have not grown immune to.

Weevils, when you wonder why there is suddenly a hole in
one of your best grown leaves, or chunks missing out of
its margin, then most likely you have weevils, arm
yourself with a bottle of something suitable from the
garden centre and follow the instructions.
Its no use spraying the once, you must have strict
regime of spraying every 5 days or so over a period of
three weeks to eradicate most pests and their eggs as
they hatch.

Common Scale.
There are two types of scale which you are likely to
encounter when growing orchids;- The first one attacks
Phalaenopsis in particular, and can migrate to most
other soft leaved plants, look on the underside of the
leaves for these hard brown limpet like creatures, if
you have only one or two, wipe them off with a cloth
soaked in methylated spirits, or resort to a systemic
insecticide regime as mentioned in the above paragraph,
systemic insecticides act by being absorbed into the
plant tissue, effectively making the plant poisonous to
its attacker, but they should be used with care, do not
exceed the stated dosage to avoid damaging the plant.
The other can be very nasty, and primarily has a taste
for Cattleyas and their cousins, but can adapt to
devouring other orchids such as Vanda's, this is:-

Boisduval scale.
A very fancy name for a real horror, you may notice flat
round scales on the underside of the leaves, which if
left unattended will produce a whole shipment of what
appears at first to be a white fungus or mealybug, these
are the nymphs by the thousand, and they are setting off
to desiccate the rest of you collection.

The trouble we have in the UK is that it is a tropical
insect, and many of our pesticides do not treat the
problem, one we have found to be of use recently is
Doff, you may have to search around to find it, it is
very effective against this type of scale, and several
other pests as well, you will probably have to give the
plant a good cleaning after a couple of weeks or so for
aesthetics. Prior to treatment, take an old toothbrush,
dipped in methylated spirits, and having removed any old
sheaths ( papery coverings from around the pseudobulbs),
scrub gently to remove the majority of the adults.

Mealybug
Usually appears as a cotton wool ball around leaf axils,
or inside the sheaths of new shoots, the above fungicide
pesticide soon sees them off, but again if its very
localized, then methylated spirits on a cotton bud sees
them off wonderfully.

Thrips, greenfly, blackfly, spider mite.
They all find a niche somewhere, the latter is another
difficult customer to deal with, and in addition to
spraying, it is a good idea to wipe the leaves and stems
of infected plants with a methylated spirit soaked
cloth, every few days if necessary to kill the eggs.

SPOTS AND DISEASES.
Orchids can fall foul of leaf rot, mildew, botrytis and
many other pathogens, by and large, providing there is a
good air movement around the plant, and that by
nightfall the leaves are fairly dry, then fungal
infections should not be a problem, and correction of
the bad condition, along with a fungal spray (check with
the garden centre that it is safe for orchids) should do
the trick, a fast fix for a localized leaf infection is
to dust a little cinnamon onto the infected area ! It is
very difficult if you have a plant suffering from a
virus disease to identify which particular type it is,
and most likely a useless exercise anyway, as viruses
are almost impossible to cure, thankfully, providing you
are hygienic around the growing area, and that any tools
used on the plants are thoroughly sterilized after use
between different plants, you should not encounter this
type of problem. Return to top of page

Firstly its important to remember that what may
appear to be a virus could be just a symptom of bad
culture.

Viruses are the most widespread disease problems
affecting orchids and fortunately most of them are rare
and in many cases hardly cause symptoms. Only a few
orchid viruses are
common and can cause problems, the two most important of
these are Cymbidium mosaic virus (CymMV) and
Odontoglossum ringspot virus (ORSV). These viruses are
found throughout the world and have a wide host range,
affecting many orchid genera.

CymMV virus infection causes leaves to show a mosaic
pattern of light and dark green areas, or black/brown
necrotic spots often appearing as a line with sunken
areas on both sides, Petals may develop lines of
necrotic spots, however floral symptoms may be delayed
up to 10 days after opening, so healthy appearing
flowers may be sold on.

ORSV virus infection causes necrotic spots, sunken areas, chlorotic streaks, line patterns and ring spots on
leaves and stems. Cattleyas and their hybrids display
colour breaks with irregular streaks of pigmentation.
Floral symptoms render the plant valueless, while the
leaf symptoms make it unattractive as a house plant.
Both viruses are easily transmitted from plant to plant
by contaminated cutting tools, work surfaces, used pots
and hands. Therefore, if an infected plant is added to
a collection, the virus can easily be spread to healthy
plants through propagation and other normal day-to-day
plant care practices.

Both these viruses which affect orchids are very stable and lose their
infectivity very slowly, so sap from an infected plant
that has dried onto tools, pots or benching provides an
excellent source of infection. They can remain
infectious for weeks or longer under the right
conditions. The greatest risk of spread is via
vegetative propagation from an infected mother plant and
is the easiest way to find yourself with more virus infected
plants. If plants to be meristemmed are displaying
suspicious symptoms, they should always be tested for
viral infection first, before introduction to a
greenhouse.

Should be carried out giving due consideration to
the instructions for use and safety provided by the
manufacturers of the control substances we list below;
solutions which we have used and found to be
satisfactory for ourselves, the decision to try one or
more of these in your environment must be yours and made
under your own responsibility.

It is always a good
idea to try and remove as many of the pests and their
eggs a possible before applying insecticides, pure
methylated spirits (not surgical spirit) is excellent
for this purpose, apply a little on a cloth and wipe
both sides of the leaves, for the less aggressive pests
this alone can be a cure in itself.

Don't expect a one off cure, several applications given over a period
of three weeks at five day intervals may be needed. do not use more
than one insecticide at a course of treatment or you may build up
resistance to it.

One fairly general and quite successful insect killer
for orchids is Provado Ultimate Bug Killer, in the spray can, rather than as
a liquid, for some reason this appears to have a
terminal effect on many orchid pests which do not
succumb readily to the liquid variety and offers better
control of spider mite; it is safe to
use on most house plants, providing you follow
the instructions, and once again, several
applications given at 5 days intervals is
recommended for the best success rates.

One home made cure can be produced in the kitchen if
you want a non toxic insecticide, here is the recipe for
you to try at your own risk :- Six heaped teaspoons of
ascorbic acid (vitamin C.) three teaspoon of plant
friendly detergent (non ionic) and a pint of water,
spray onto aphids and suchlike, the mixture will kill
any insects which absorb oxygen through their skin, but
not their eggs. As prevention is always better than a
cure, treat new plants with respect, quarantine them if
possible, try not to let intake fans suck air in from
anywhere near a flower border or hedge, and always be
prepared to sacrifice a "well infected" plant for the
sake of the rest. It will not work on all pests
Return to top of page

PROBLEM

TREATMENT

Viral infections

Virused plants have no place in the greenhouse,
but unless the virus spoils the visual quality of the plant, a
single isolated one may be used as a houseplant. whilst viruses
cannot be treated many plants first thought to be virused will test
negative.

Weevils

Bifenthrin, Thiacloprid - in the UK try Provado
Vine Weevil Killer

Spider mites (see below)

Bifenthrin, Pirimiphos methyl,, Malathion
Rotenone- long term increase humidity it is difficult to eradicate
these pests without a specific insecticide, most of which are
currently banned for home use, try anything that says it will cure,
but be prepared for a long battle, and keep up with treatment, to
get newly hatched mites as they appear. in the uk Try Bio Liquid
Derris Plus or Bug Free

Slugs and snails

Metaldehyde, Methiocarb, Aluminiumsulphate -

Common scale

You should find a suitable insecticide at you
local garden centre or use, Insecticidal soap to wash the pests off.

Boisduval scale

Imidacloprid and Methiocarb, Sulphur and fatty
acid mixture in the UK you could try Provado Ultimate Bug Killer but
it must be the in the can formula ( see above ad.) or
Doff

Spider mites like dry conditions, and can be difficult to eradicate, if
you only have an infestation on one plant, make life unpleasant for
them, water the plant, and place it in a clear plastic bag, blow the bag
up with your mouth and tie off, leave the plant there for a few days or
so as long as it does not appear stressed, the humidity which will build
up inside the bag will create a hostile environment for the mites, but
of course their eggs may survive, and you may have to repeat the several
times to eradicate them.

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